The present invention relates to recording objective information into such recording media as optical disks, and, in particular, to the recording capable of detecting erroneous recording of information (that is, recording of different information from objective information) prior to the actual recording.
In general, for recording objective information (i.e., information to be recorded) into recording media, such as optical disks, a recording clock signal synchronous with travel speeds of recording media is used so that recording pits are formed which accurately correspond in sizes to the content of the information to be recorded.
When the recording is carried out with a CD-R (Compact Disk-Recordable), which had been a general type of recordable optical disk, a recording clock signal whose frequency is set to a reference frequency for controlling the rotation of the CD-R is output from a clock signal generator constructed by having a crystal oscillator and used for the recording.
To the contrary, a DVD-R (DVD-Recordable) has been intensively developed which has a packing density approximately seven times larger than the CD-R. Owing to the raised packing density, the DVD-R needs to increase accuracy in recording positions thereon compared to the CD-R.
In such case that the recording clock signal thus-generated is used in recording for the DVD-R, the DVD-R may have some disturbance that causes its disordered rotation. In such state, the DVD-R rotation speed and the recording clock signal frequency is out of synchronization, resulting in an inaccurate recording operation.
Thus, a countermeasure against the problem is taken such that a synchronizing signal pre-recorded in the DVD-R which has not undergone any information recording yet is detected to yield a recording clock signal based on the synchronizing signal, and even when the DVD-R rotation deviates from the steady speed due to any disturbance, the recording clock signal frequency is also made to shift depending on the deviations in the DVD-R rotation speed. In consequence, the frequency of the recording clock signal always synchronizes with the rotation speed of the DVD-R.
However, in this type of information recording apparatus, there is the possibility that the synchronizing signal cannot be detected accurately, owing to, for example, defects formed on the DVD-R, such as scratches or fingerprints. If such case happens, the processing for yielding the recording clock signal is influenced, thereby leading to inaccurate recording of information to be recorded.
Accordingly, it is an object of the present invention to provide a technique for detecting erroneous recording of information, which detects an synchronous state between the rotation speed of an optical disk and the frequency of a recording clock signal, the state being brought about in occasions which the synchronizing signal cannot be detected accurately from the optical disks, and senses a possibility of causing erroneous recording in advance, thus being able to take appropriate measures for it. The detecting technique is practiced into a method and apparatus for detecting erroneous recording and a method and apparatus for recording information which employ the technique for detecting erroneous recording.